ZITHROMAX 400/MG/10/ML 30/ML SUSP

Indications

Approved Uses

Approved (typical labeling): community-acquired pneumonia; acute bacterial exacerbation of chronic bronchitis/COPD; acute bacterial sinusitis; pharyngitis/tonsillitis (when appropriate, often as alternative therapy); uncomplicated skin and skin structure infections; uncomplicated urethritis and cervicitis due to Chlamydia trachomatis; genital ulcer disease (chancroid) due to Haemophilus ducreyi; pediatric acute otitis media.

Off-Label Uses

Common off-label uses include Mycobacterium avium complex (MAC) prophylaxis/treatment (often with other agents), pertussis treatment/post-exposure prophylaxis, certain chlamydial infections beyond labeled sites, and selected atypical respiratory infections per local guidance; COVID-19 is not recommended (lack of benefit). Typhoid fever is not a standard off-label use in guidelines where resistance is prevalent and better options exist.

Dosage & Administration

Dosing by Condition

Adults: CAP 500 mg day 1 then 250 mg daily days 2-5; acute bacterial sinusitis 500 mg daily x3 days; AECB/COPD 500 mg day 1 then 250 mg daily days 2-5 OR 500 mg daily x3 days; uncomplicated skin/skin structure 500 mg day 1 then 250 mg daily days 2-5; NGU/cervicitis (Chlamydia) 1 g once. Pediatrics (oral suspension): acute otitis media 30 mg/kg once OR 10 mg/kg daily x3 days OR 10 mg/kg day 1 then 5 mg/kg days 2-5; pharyngitis/tonsillitis 12 mg/kg daily x5 days (max 500 mg/day). Gonorrhea: azithromycin monotherapy 2 g once is not recommended in current guidelines; if used historically, it was as part of older regimens and is generally avoided due to resistance and GI intolerance.

Initial Dose

500mg on Day 1 (adults, most indications)

Maintenance Dose

250 mg once daily on Days 2 through 5.

Maximum Dose

2g as a single dose (for gonorrhea); 500mg/day for standard courses

Children's Dosage

Otitis media: 30mg/kg as single dose OR 10mg/kg/day for 3 days OR 10mg/kg on Day 1 then 5mg/kg/day for 4 days (max 500mg/day). Community-acquired pneumonia: 10mg/kg on Day 1 (max 500mg), then 5mg/kg/day Days 2-5 (max 250mg/day). Pharyngitis: 12mg/kg/day for 5 days (max 500mg/day). Not recommended in children under 6 months

Dose Adjustment Notes

Renal: no adjustment generally needed in mild-moderate impairment; use caution in severe renal impairment (e.g., CrCl/GFR <10 mL/min). Hepatic: no specific adjustment, but use caution/avoid if significant hepatic disease or prior azithromycin-associated cholestatic jaundice/hepatic dysfunction; elderly: no routine adjustment, but assess QT-risk and organ impairment.

How to Take

Reconstitute with water as directed; shake well before each dose; measure with an oral syringe/medicine spoon; may be taken with or without food; if GI upset occurs, take with food; avoid aluminum/magnesium antacids within 2 hours; complete the prescribed course.

How to Prepare

Reconstitute by adding the labeled amount of water to the bottle (often in two portions), shaking well after each addition, to a final volume of 30 mL; shake well before each dose.

Side Effects

Common Side Effects

Diarrhea, nausea, abdominal pain, vomiting; less commonly headache and dizziness.

Side Effect Frequency

Common: diarrhea/loose stools, nausea, abdominal pain, vomiting; less common: headache, dizziness, rash; rare but serious: QT prolongation/arrhythmias, hepatotoxicity/cholestatic hepatitis, severe hypersensitivity (including SJS/TEN), and hearing disturbances.

Safety & Warnings

Contraindications

Contraindicated in patients with hypersensitivity to azithromycin, erythromycin, or any macrolide/ketolide; and in those with a history of cholestatic jaundice/hepatic dysfunction associated with prior azithromycin use.

Warnings & Precautions

Warnings/precautions: QT prolongation risk (avoid/monitor in patients with known QT prolongation, electrolyte abnormalities, bradycardia, or on QT-prolonging drugs), severe hypersensitivity/SCAR (stop immediately if suspected), hepatotoxicity (stop if signs of liver injury), C. difficile-associated diarrhea, possible exacerbation of myasthenia gravis, and superinfection with prolonged use.

Age Restriction

Generally approved for pediatric use from 6 months of age and older for certain indications; not recommended in infants <6 months due to limited safety/efficacy data (except specific indications per label).

Driving Warning

Safe

Drug Interactions

Drug Interactions

Key interactions: aluminum/magnesium antacids (separate dosing to avoid reduced azithromycin peak levels), warfarin (monitor INR), digoxin (monitor levels/toxicity), cyclosporine (monitor levels), nelfinavir (increases azithromycin exposure), and other QT-prolonging drugs (additive arrhythmia risk); avoid ergot derivatives (ergotism risk).

Interaction Severity

MAJOR/AVOID: pimozide; ergotamine/dihydroergotamine (ergotism risk); other high-risk QT-prolonging agents (e.g., amiodarone, sotalol, certain antipsychotics) in susceptible patients. MODERATE: warfarin (monitor INR), digoxin (monitor levels/clinical toxicity), cyclosporine (monitor levels), nelfinavir (↑ azithromycin exposure). MINOR: aluminum/magnesium antacids (↓ Cmax-separate by 2 hours).

Food Interaction

May be taken with or without food; taking with food can improve tolerability; separate aluminum/magnesium-containing antacids by at least 2 hours.

Alcohol Interaction

Safe

Special Populations

Pregnancy

Category B (No evidence of risk in animal studies; inadequate human data)

Breastfeeding

Caution

Children

Otitis media: 30mg/kg as single dose OR 10mg/kg/day for 3 days OR 10mg/kg on Day 1 then 5mg/kg/day for 4 days (max 500mg/day). Community-acquired pneumonia: 10mg/kg on Day 1 (max 500mg), then 5mg/kg/day Days 2-5 (max 250mg/day). Pharyngitis: 12mg/kg/day for 5 days (max 500mg/day). Not recommended in children under 6 months

Elderly

Standard adult dosing - no routine dose adjustment required. Use with caution if significant renal or hepatic impairment is present

Kidney Impairment

No dose adjustment needed for mild to moderate renal impairment (e.g., GFR/CrCl >10 mL/min); use with caution in severe renal impairment (GFR/CrCl <10 mL/min).

Liver Impairment

No specific dose adjustment is recommended for mild to moderate hepatic impairment, but use with caution; avoid/use only if benefits outweigh risks in severe hepatic disease and discontinue if signs of hepatitis/cholestasis occur.

Storage & Patient Advice

Storage Conditions

Store unreconstituted powder below 30°C. After reconstitution: store at room temperature (below 30°C); do not refrigerate or freeze; discard any unused suspension after 10 days.

Preparation Instructions

Reconstitute by adding the labeled amount of water to the bottle (often in two portions), shaking well after each addition, to a final volume of 30 mL; shake well before each dose.

Missed Dose

Take the missed dose as soon as remembered; if it is close to the next scheduled dose, skip the missed dose and continue the regular schedule; do not double doses.

Stopping the Medicine

Complete the full prescribed course; no taper is required-stop when the prescribed duration is finished unless a serious adverse reaction occurs and a clinician advises stopping early.

Overdose

Symptoms may include nausea, vomiting, diarrhea/abdominal pain and reversible hearing impairment; management is supportive/symptomatic (consider activated charcoal if recent ingestion) and seek urgent medical attention-no specific antidote.

Patient Counseling

Reconstitute exactly as directed; shake well before each dose and measure with an oral syringe/spoon; take with or without food (with food if stomach upset); finish the full course; avoid aluminum/magnesium antacids within 2 hours; seek care for severe/persistent diarrhea, rash/allergic reaction, jaundice/dark urine, or palpitations/syncope (QT risk); store as directed on the label and discard after the labeled in-use period; keep at/under 30°C per SFDA storage condition.

Monitoring Requirements

No routine labs for short courses in low-risk patients; monitor for clinical response and diarrhea; check LFTs if hepatic disease or symptoms of hepatotoxicity occur; consider ECG/QT risk assessment (and ECG if high risk or on QT-prolonging drugs); monitor INR if on warfarin and digoxin levels/clinical toxicity if on digoxin.

Pharmacology

Mechanism of Action

Binds to the 50S ribosomal subunit (23S rRNA) of susceptible bacteria, inhibiting translocation/protein synthesis and thereby inhibiting bacterial growth (primarily bacteriostatic).

Onset of Action

Pharmacokinetic onset: peak plasma concentrations typically occur about 2-3 hours after an oral dose; clinical improvement in bacterial infections is usually seen within 24-72 hours if the pathogen is susceptible.

Duration of Effect

Because of extensive tissue distribution and a long terminal half-life, antibacterial activity/therapeutic tissue concentrations can persist for several days after the last dose.

Half-Life

Terminal elimination half-life: approximately 68 hours.

Bioavailability

Approximately 37% (oral azithromycin; suspension/capsules are similar).

Metabolism

Limited hepatic metabolism (e.g., N-demethylation); not a clinically significant CYP450 substrate and has minimal CYP-mediated interaction potential compared with other macrolides.

Excretion

Primarily biliary excretion with fecal elimination; renal excretion is minor (about 6% of dose as unchanged drug).

Protein Binding

Concentration-dependent protein binding, approximately 7% to 51%.

Product Information

Available Dosage Forms

For azithromycin (Zithromax/azithromycin products): powder for oral suspension (this product per verified API), oral tablets, and IV powder for solution/infusion; ophthalmic eye drops are not a Zithromax azithromycin dosage form (azithromycin ophthalmic is a different product/brand in some markets).

Composition per Dose

Each 5ml (after reconstitution): 200mg azithromycin (40mg/ml)

Generic Availability

Yes

OTC Alternatives

No OTC alternative - prescription required for all antibiotic therapy

Spectrum

Broad-spectrum

Antibiotic Class

Macrolide

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